1. Field of the Invention
The present invention is directed to support elements for short arc lamp electrode rods. More specifically, such support elements of the present invention are metal and provide significant passage areas for circulation of gas within the arms of the lamp.
2. Prior Art Statement
Short arc lamps have been in use for many years and typically involve xenon or other gas within a quartz glass envelope with an anode and cathode separated by a gap across which an arc passes during use. Xenon is particularly useful because it emits a daylight-like discharge.
The electrodes are attached to electrode rods in opposite positions to each other and these rods extend into quartz arms for contact with electrical connectors. The electrode rods are supported so as to be centrally located axially within the quartz arms, and so as to align the electrodes with one another.
U.S. Pat. No. 4,559,472 describes a discharge lamp or arc lamp with specified support element structures for the electrode rods (referred to as "elongated electrodes"). The high pressure arc lamp described has a quartz glass enclosure defining a discharge space and quartz arms extending away from the discharge space are provided with elongated electrodes (assemblies) extending respectively through the quartz arms. These electrode assemblies carry respective electrodes at their inner ends and the electrode assemblies are sealed hermetically to the respective envelope portion. In order to support the electrodes within the envelope, respective support elements are fitted around the electrodes in spaced relation to the envelope and quartz arms. Means including a respective resilient element engaging each support member, are provided to hold the support elements in their axial position around the respective electrode assemblies. The resilient elements are each held between the respective electrode and the inner surface of the respective support element to continuously urge the axially outer surface of the support element resiliently against the respective inner diameter of the quartz arms.
Unfortunately, the lamp described in U.S. Pat. No. 4,559,472 above retains the gases within the bulbous portions or bulb of the envelope and the sputtering and blackening which occurs limits the illumination and the life of the lamp.
U.S. Pat. No. 4,463,281 describes another arc lamp wherein the electrode rods are supported by spring biased quartz plugs. These plugs are of less mass than the previously described prior art electrode supports and are spring loaded toward the center, with notches or openings cut out for gas to flow through. However, these spaces do not permit or induce significant enough gas flow to substantially reduce the negative sputtering effects described above. In fact, larger cut outs cannot be made without causing or risking cracking or shattering of the glass supports.
Thus, while various supports have been developed for short arc lamp electrode rods, none suggest or teach the present invention metallic supports with their configurations and advantages described herein.